Multi-level step-down voltage converters have more than two switches and one or more flying capacitors as a switching stage, and an inductor-capacitor (LC) filter as an output stage.
A drawback of these converters is an intrinsic instability of the flying-capacitor voltage under Peak Current Mode Control (PCMC). The instability associated with the flying-capacitor voltage in PCMC should not be confused with sub-harmonic oscillations, which is also found in step-down converters under PCMC, and can be suppressed using a compensation ramp. The flying-capacitor voltage instability is a separate phenomenon which naturally occurs under PCMC, and also under voltage-mode control, whenever there is a mismatch between switching groups or their driving signals. Flying capacitor voltage unbalance does not occur in a multi-level converter under Valley Current Mode Control (VCMC).